This invention relates to processing of audio and, more particularly, to processing of audio for presentation to loudspeakers.
The spatial images of soundfields are mainly detected through interaural time differences (ITD) and interaural delay differences (ILD). For low frequency signals, i.e., below 500 Hz, synchronous binaural detection provides imaging cues. For signals above 2 kHz, where “synchronous” detection is not neurally possible, the ear switches from phase to envelope detection. Accordingly, at the higher frequencies the ILD and leading edges of the envelope provide the imaging cues. Between 500 Hz and 2 kHz, both systems contribute imaging cues, but sometimes those cues conflict.
When audio is recorded, both direct and indirect sound is captured by the microphones and converted to a composite electrical signal. To reproduce the sound, the electrical signals are converted to sound, but the prior art pays no attention to the sound field imaging cues that are contained in the signal. There is prior art, however, that applies some of the signal to a directional speaker, and applies the remaining signal to a diffusing speaker, but the ratio of the signals that are applied to the two different speakers is fixed, or manually adjustable. It is not sensitive to the signal characteristics.